個人計算機領域流行用智能電池，這是因為智能電池能提供本個工業標準、高精度氣壓計（gasgauge）系統。智能電池符合智能電池供電系統（SBS）所定義的元件所有工作性能指標，電池具有跟蹤有關電池充電和使用信息的嵌入控制器。通過串行、2線SMBus接口提供信息到系統。可詢問電池信息包括剩余容量、總容量、在現有放電速率下時間余、放電電流、終端電壓等。由于大多數智能電池在總線中可成為主機，所以電池可控制智能電池充電器使其最佳充電。Linear公司LTC1759智能電池充電器IC設計用于控制這類智能電池。另外，由電(dian)池(chi)提(ti)供的安(an)全信號指示電(dian)池(chi)是(shi)(shi)否(fou)呈現(xian)在(zai)系統(tong)中(zhong)和是(shi)(shi)否(fou)有熱引起(qi)的告警或在(zai)其他系統(tong)失(shi)效時是(shi)(shi)否(fou)電(dian)池(chi)失(shi)效。SBS顯(xian)著(zhu)特點是(shi)(shi)安(an)全、使(shi)用(yong)容易(yi)和兼容性。

　　SBS規范允許兩種類型智能電池充電器（SBC）：Level2充電和Level3充電器。Level2充電器（如LTC1759）是SMBus上的從機，響應來自電池的命令控制充電。Level3充電器可以是SMBus上的主機或從機，它可詢問電池確定充電信息。SBC與電池化學類型無關。它響應來自電池的命令提供充電電流和充電電壓。電池的零電流（或零電壓）或終止充電報警形式發出充電終止。假若安全信號指標電池不存在或安全充電電池太熱，則(ze)充電也將終止。

　　SMBus 為系(xi)統(tong)和(he)電(dian)源(yuan)(yuan)管(guan)理這(zhe)樣的(de)(de)(de)(de)任務提供(gong)了一(yi)條控制總線，使用(yong)(yong) SMBus 的(de)(de)(de)(de)系(xi)統(tong)，設(she)(she)備(bei)之間發送和(he)接收消息都是(shi)(shi)通過 SMBus，而(er)不是(shi)(shi)使用(yong)(yong)單獨的(de)(de)(de)(de)控制線，這(zhe)樣可(ke)以節省(sheng)設(she)(she)備(bei)的(de)(de)(de)(de)管(guan)腳(jiao)數。 　　使用(yong)(yong) SMBus，設(she)(she)備(bei)還(huan)可(ke)以提供(gong)它的(de)(de)(de)(de)生產(chan)信息，告訴(su)系(xi)統(tong)它的(de)(de)(de)(de)型號，部件(jian)(jian)號等，針對掛起事(shi)件(jian)(jian)保存(cun)它的(de)(de)(de)(de)狀(zhuang)態(tai)，報告不同類別的(de)(de)(de)(de)錯誤，接收控制參數，并返回它的(de)(de)(de)(de)狀(zhuang)態(tai)等。 　　SMBus器(qi)(qi)件(jian)(jian)存(cun)在(zai)現(xian)有7層(ceng)OSI網絡模型中的(de)(de)(de)(de)前3層(ceng)，即(ji)物理層(ceng)，數據鏈(lian)路層(ceng)和(he)網絡層(ceng)。 　　SMBus最初的(de)(de)(de)(de)目(mu)的(de)(de)(de)(de)是(shi)(shi)為智能電(dian)池，充(chong)電(dian)電(dian)池和(he)與其他系(xi)統(tong)通信的(de)(de)(de)(de)微控制器(qi)(qi)之間的(de)(de)(de)(de)通信鏈(lian)路而(er)定義的(de)(de)(de)(de)。SMBus也被用(yong)(yong)來連接各(ge)種(zhong)設(she)(she)備(bei)，包(bao)括(kuo)電(dian)源(yuan)(yuan)相關(guan)設(she)(she)備(bei)，系(xi)統(tong)傳感器(qi)(qi)，EEPROM通訊設(she)(she)備(bei)等等。

　　LTC1759是一款完整的Level2智能電池充電器。它能在SMBus接口上用接收和譯碼命令自動充電智能電池。LT1759遵從智能電池充電器規范的全部(bu)安(an)全要求(qiu)，包括3分鐘定(ding)時器（保護(hu)(hu)SMBus通(tong)信換效和喚醒(xing)模式期(qi)間鋰離子電池過充電）。硬件可(ke)編程電注和電壓限制提供另外等(deng)級保護(hu)(hu)，這種保護(hu)(hu)由失效軟件不(bu)可(ke)能改(gai)變。

　　LTC1759管理智能電池充電系統的所有復雜事物。它具有SBC依從性、安全、輸出電壓精確、SMBus加速泵、墻式適配器電流限制等特性。它把智能充電器的恒流（CC）、恒壓（CV）、電流模式開關電池充電器電路融合于一身。

　　電路描述

　　LTC1759包括：一個同步、電流模式、PWM降壓開關控制器，一個充電器控(kong)制(zhi)器，兩個(ge)控(kong)制(zhi)充(chong)電器參(can)量的10位DAC，一個(ge)熱敏電阻安全信號譯碼器，硬(ying)件電壓和電流限(xian)制(zhi)譯碼器和一個(ge)SMBus控(kong)制(zhi)器單(dan)元（見圖1）。

 智(zhi)能電(dian)(dian)池(chi)或系統控制器(qi)通過SMBus接(jie)口命(ming)令(ling)對恒漢和恒壓(ya)限值進行編程。降壓(ya)變壓(ya)器(qi)用N-溝MOSFET做為開關(guan)，使成本降低、高效(xiao)率工作。熱敏電(dian)(dian)阻安(an)全檢測電(dian)(dian)路檢測電(dian)(dian)池(chi)存在或確定電(dian)(dian)池(chi)溫度是否(fou)允許安(an)全充電(dian)(dian)。

當通過SMBus傳輸(shu)接(jie)(jie)收(shou)(shou)恒(heng)流(liu)(liu)(liu)值(zhi)時(shi)，它(ta)被RILIMIT定標和限制到(dao)低于編程值(zhi)。此(ci)(ci)修正(zheng)值(zhi)編程電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)DAC，設置DC充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)。電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)DAC是10位△∑DAC，當希(xi)望充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)時(shi)，它(ta)從PROG引(yin)腳吸收(shou)(shou)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)（見(jian)圖2）。放(fang)大(da)器PROG引(yin)腳吸收(shou)(shou)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)（見(jian)圖2）。放(fang)大(da)器CAI感測RSENSE上的壓降并使此(ci)(ci)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓跨接(jie)(jie)到(dao)RS2（200Ω）；流(liu)(liu)(liu)經RS2的電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)通過電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)鏡(jing)像做為PROG引(yin)腳上的上接(jie)(jie)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)。流(liu)(liu)(liu)經RS2電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)與來自PROG引(yin)腳電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)相匹配由CA2實現恒(heng)流(liu)(liu)(liu)工作。由于DAC輸(shu)出(chu)是一(yi)串脈沖，所以(yi)需要(yao)平滑電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)器對脈沖濾(lv)波使其變為DC。

  LTC1759需要(yao)兩個(ge)電(dian)(dian)源(yuan)。PWM電(dian)(dian)路在墻式適配器電(dian)(dian)源(yuan)斷開(kai)時直接(jie)通過Vcc引腳運(yun)行，邏(luo)輯功(gong)能(neng)運(yun)行與VDD電(dian)(dian)源(yuan)無(wu)關(guan)。PWM電(dian)(dian)路在去掉(diao)AC電(dian)(dian)源(yuan)時能(neng)進入40μA微功(gong)率停機模式，使邏(luo)輯和(he)(he)SMBus工作(zuo)(zuo)能(neng)保持運(yun)行，這是Intel ACPI標準所需要(yao)的。這種分離電(dian)(dian)源(yuan)也使邏(luo)輯和(he)(he)SMBus能(neng)根據系統設計為(wei)員的需要(yao)運(yun)行在3V和(he)(he)5V.為(wei)使LTC1759邏(luo)輯功(gong)耗最小，邏(luo)輯電(dian)(dian)流由時鐘電(dian)(dian)路激勵，時鐘電(dian)(dian)路當無(wu)動作(zuo)(zuo)時停機并蘇醒服務于SMBus動作(zuo)(zuo)或產生(sheng)中(zhong)斷。一旦請求服務，LTC1759便返(fan)回到休(xiu)眠(mian)。

　　當去(qu)掉AC電(dian)源(yuan)或(huo)去(qu)掉電(dian)池時(shi)，通(tong)(tong)過(guo)CHGEN-SDB引腳(jiao)組(zu)合發(fa)生PWM停(ting)機。LTC1759通(tong)(tong)過(guo)DCDIV通(tong)(tong)腳(jiao)檢測(ce)AC損耗。閾值通(tong)(tong)常設置恰好低于墻式(shi)適配的最小(xiao)有(you)效電(dian)壓。AC電(dian)源(yuan)狀態通(tong)(tong)過(guo)SMBus可(ke)由系統讀出(chu)。UV引腳(jiao)只用于置PWM電(dian)路進入微功率停(ting)機狀態，它直接連(lian)到墻式(shi)適配器(qi)電(dian)源(yuan)。

　　在(zai)設計中電感器(qi)選(xuan)擇不是(shi)關鍵(jian)，這(zhe)是(shi)因為充(chong)電器(qi)的(de)(de)環路響應在(zai)意地設置很慢。實際的(de)(de)低限值(zhi)為15μH左右，低值(zhi)電感器(qi)將產生較(jiao)高的(de)(de)紋波(bo)電流，在(zai)輸出需要較(jiao)低ESR電容(rong)器(qi)。

　　輸出(chu)(chu)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)的(de)選擇對ESR（等效串(chuan)(chuan)聯電(dian)(dian)(dian)(dian)(dian)阻）不(bu)是很苛刻，但(dan)必須處理來自充電(dian)(dian)(dian)(dian)(dian)器(qi)的(de)所有(you)(you)紋(wen)波電(dian)(dian)(dian)(dian)(dian)流。不(bu)用(yong)(yong)(yong)考慮電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)的(de)紋(wen)波電(dian)(dian)(dian)(dian)(dian)流，因為(wei)(wei)充電(dian)(dian)(dian)(dian)(dian)器(qi)有(you)(you)效阻抗(kang)遠(yuan)遠(yuan)大(da)于電(dian)(dian)(dian)(dian)(dian)感器(qi)的(de)ESR。很多(duo)電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)組具有(you)(you)內部串(chuan)(chuan)聯保護MOSFET，這提高了(le)電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)ESR。在(zai)(zai)多(duo)電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)配(pei)置(zhi)中(zhong)也有(you)(you)與電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)串(chuan)(chuan)聯的(de)功率路由(you)MOSFET，進(jin)一(yi)步增加了(le)電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)ESR。從充電(dian)(dian)(dian)(dian)(dian)器(qi)觀點，輸入電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)器(qi)ESR可高達(da)1Ω，使電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)器(qi)選擇范圍寬。當(dang)采(cai)用(yong)(yong)(yong)電(dian)(dian)(dian)(dian)(dian)阻或電(dian)(dian)(dian)(dian)(dian)子負載時，可能會(hui)發生某種不(bu)穩定(ding)(ding)性。增加300Ω電(dian)(dian)(dian)(dian)(dian)阻器(qi)與PROG引腳電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)器(qi)串(chuan)(chuan)聯或在(zai)(zai)輸出(chu)(chu)置(zhi)10μF電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)器(qi)能改善穩定(ding)(ding)性。在(zai)(zai)輸出(chu)(chu)不(bu)需(xu)要用(yong)(yong)(yong)陶(tao)瓷(ci)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)器(qi)，因為(wei)(wei)在(zai)(zai)很輕(qing)負載電(dian)(dian)(dian)(dian)(dian)流聲頻(pin)下(xia)開關變(bian)(bian)換器(qi)變(bian)(bian)得不(bu)連接和在(zai)(zai)下(xia)降周期開始時電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)器(qi)會(hui)造(zao)成噪(zao)聲，應該(gai)采(cai)用(yong)(yong)(yong)鉭電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)。輸入電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)選擇由(you)充電(dian)(dian)(dian)(dian)(dian)器(qi)輸入紋(wen)波電(dian)(dian)(dian)(dian)(dian)流（一(yi)般為(wei)(wei)最大(da)輸出(chu)(chu)電(dian)(dian)(dian)(dian)(dian)流的(de)1/2）決定(ding)(ding)。對于4A充電(dian)(dian)(dian)(dian)(dian)器(qi)建議用(yong)(yong)(yong)22μF（50V）陶(tao)瓷(ci)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)器(qi)，它(ta)一(yi)般可處理2A紋(wen)波電(dian)(dian)(dian)(dian)(dian)流。

　　從電(dian)(dian)(dian)池(chi)(chi)到墻(qiang)式(shi)(shi)適配器的電(dian)(dian)(dian)流保護由P-溝MOSFET（Q1）提供(gong)。電(dian)(dian)(dian)壓(ya)比較(jiao)器監控(kong)跨接在(zai)MOSFET上的電(dian)(dian)(dian)壓(ya)而(er)且(qie)當墻(qiang)式(shi)(shi)適配降到電(dian)(dian)(dian)池(chi)(chi)電(dian)(dian)(dian)壓(ya)之上小于(yu)200mV時關閉(bi)MOSFET。盡管價廉的二極管可用于(yu)替代以MOSFET，但(dan)MOSFET只(zhi)增(zeng)加(jia)100mV到0.4V低(di)壓(ya)差工作模式(shi)(shi)而(er)不產生(sheng)額外的熱量。在(zai)沒有(you)電(dian)(dian)(dian)池(chi)(chi)起動時間(jian)，采用MOSFET附加(jia)二極管使墻(qiang)式(shi)(shi)適配器電(dian)(dian)(dian)源(yuan)能達(da)到Vcc引腳并為PWM控(kong)制電(dian)(dian)(dian)路供(gong)電(dian)(dian)(dian)。

　　主要的補償是d PROG引腳上進(jin)行；然而DAC脈(mo)沖濾波要求確定(ding)(ding)電(dian)容(rong)器(qi)(qi)有效值。脈(mo)沖紋波電(dian)流必(bi)須小平200mV或環(huan)路起伏（在(zai)輕(qing)載充電(dian)電(dian)流時出現的環(huan)路不穩定(ding)(ding)性）。Vc引腳電(dian)容(rong)器(qi)(qi)的主要功能是提供(gong)自啟動支持。必(bi)須有一個(ge)1.5K電(dian)阻器(qi)(qi)與(yu)Vc引腳電(dian)容(rong)器(qi)(qi)串聯(lian)以能恰當(dang)停機。

　　從熱(re)觀點(dian)考慮，輸出電(dian)壓在電(dian)池溫度充電(dian)范圍內(nei)保持大約(yue)0.5%精度。精度越(yue)高，電(dian)流充電(dian)容(rong)量就越(yue)大，而更(geng)重(zhong)要是在電(dian)池中與電(dian)壓基充電(dian)終端電(dian)路有關(guan)的(de)問題就會更(geng)少。

　　關于SMBus加速(su)泵，AC適配電流限(xian)制，安(an)全信(xin)號感(gan)測，安(an)全電壓(ya)和電流范圍設計等(deng)問(wen)題在此就不一一詳述。

　　LTC1579遵從智能電池系統組織發表的智能電池充電器標準。充電器控制器也遵從Intel的ACP標準，甚至當沒有AC墻式適配器電源時也能響應系統指令。該充電器提供最寬的電流和電壓工作范圍。LTC1759具有價廉、高性能和安全的特點，比其他智能電池充電器優越。